In the printing industry small stacks or work stacks, of paper sheets (e.g. 2-15 cm high) are separated and removed from a large or basic stack (e.g. 100 cm high) for future processing, for instance aligning, cutting, folding or printing.
During these future processing steps it is important that each sheet should be able to be separated from the rest of the sheets individually. To achieve this, introduction of air (airing) between the individual sheets is essential to avoid that neighbouring sheets “stick” together.
The basic airing process is to bend the small stack of paper sheets, the work stack, in such a way that the curvature of the stack is larger at the bottom side than at the top side, and hence a space is formed between all neighbouring sheets into which air is sucked whereby the tendency of neighbouring sheets to stick together is eliminated.
Now the work stack can be carried over to an aligning device, typically a shaking box or vibration table, where the sheet edges can be aligned because of the aeration of the work stack.
This is very labour intensive and potentially harmful to the person performing the lifting and flexing actions manually. Attempts have been made to automate this aeration process with unsatisfactory results.
Therefore, a main object of the invention is to automate the process in a more satisfactory manner so that the manual labour can be replaced by mechanical means.